Abstract A10: Radiolabelled AMD3100 for the management of malignant lymphoma: Translational study
Authors: Tamanna Lakhanpal, Jaya Shukla, Rajender Kumar, Harmanpreet Singh, Pankaj Malhotra, Alka Khadwal, Gaurav Prakash, Amanjit Bal, Yogesh Rathore, BR Mittal
Journal: Blood Cancer Discovery (2022)

Abstract Introduction: Malignant lymphomas are heterogeneous group of neoplasm comprising of proliferating lymphoid cells or their precursors. The two main types of lymphoma are Hodgkin Lymphoma and Non- Hodgkin Lymphoma. The current treatment modalities include chemotherapy; radiation therapy; passive immunotherapy; radio-immunotherapy and small-molecule inhibitors. Radiation therapy is the treatment of choice if disease is localized. Targeted therapy with antibody and small molecules may be more suitable for malignant lymphomas. Lymphoma cells are reported to over-express chemokine receptors that favors leukocyte infiltration, promotes tumorigenesis, angiogenesis, immune evasion, and metastasis. Human CXCL4 and CCL5 oligomerize with over 20 chemokine subfamilies to control leukocytes infiltration. CXCR4 antagonists disrupt the specific interaction of chemokines with CXCR4 and may elicit therapeutic potential. Chemokine receptor 4 (CXCR4) has been explored with radiolabelled CXCR4 antagonist (AMD3100) for imaging and future targeted radiation therapy for malignant lymphoma. Methods: Standardization of conjugation of AMD3100 with bifunctional chelating agents (DTPA, NOTA etc.). Optimization include radiolabelling of conjugated AMD3100 with 68Ga and 177Lu for imaging and therapeutic purpose respectively. The radionuclide and radiochemical purity of the product was determined. CXCR4 binding efficacy and toxicity studies were performed on CXCR4 expressing cancer cell-lines. The quality control of radiolabelled AMD3100 included, radiochemical purity, sterility, pyrogenicity, human serum and PBS stability. The biodistribution studies were performed in normal rats. After obtaining clearance from institutional ethics committee,68Ga-AMD3100-DTPA PET/CT was performed in lymphoma patients (n=2). The uptake was compared with 18FDG uptake for proof of concept. Results: DTPA conjugation of AMD3100 (1087 Da) and NOTA conjugation (1014 Da) was confirmed with MALDI-TOF. The radionuclide and radiochemical purity of 68Ga and 177Lu AMD3100 was &amp;gt;99%. Radio-ligand binding assay confirmed high specificity (Kd = 57.16 nM) of 177Lu-AMD3100-DTPA towards CXCR4 expressing cancer cells. Furthermore, the log absolute IC50 concentration of 177Lu-AMD3100-DTPA calculated for cytotoxicity assessment, via MTT assay, was 2.628 nM. Immunocytochemistry depicted positive nuclear staining of CXCR4 receptors in cancer cells. The synthesized radiopharmaceuticals were sterile and pyrogen-free. In-vivo physiological biodistribution of 68Ga-AMD3100-DTPA was found in liver, lung and spleen. The radiotracer showed faster renal clearance and low blood pool activity. In addition to physiological uptake, 68Ga-AMD3100-DTPA PET/CT showed similar lesions that were seen in 18FDG PET/CT of lymphoma patients. Conclusion: 68Ga/177Lu-AMD3100-DTPA demonstrated high target specificity towards CXCR4 expressing lymphoma cells. Cytotoxicity and patient study indicated its potential as theranostic agent. It can be used for the selection of patients, targeted therapy and response evaluation. Citation Format: Tamanna Lakhanpal, Jaya Shukla, Rajender Kumar, Harmanpreet Singh, Pankaj Malhotra, Alka Khadwal, Gaurav Prakash, Amanjit Bal, Yogesh Rathore, BR Mittal. Radiolabelled AMD3100 for the management of malignant lymphoma: Translational study [abstract]. In: Proceedings of the Third AACR International Meeting: Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2022 Jun 23-26; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2022;3(5_Suppl):Abstract nr A10.